How to dig a 1-mile tunnel under the North Side of Chicago

What's a good way to divert floodwaters from the North Branch of the Chicago River? Dig a deep, deep tunnel to divert the water. That is the gist of the project underway in Albany Park, a neighborhood that saw significant flooding in 2008 and 2013. The tunnel, 150 feet below Foster Avenue, will cost $70 million and is scheduled to be completed by April 2018.

WHERE DOES IT FLOOD?

The North Branch flows along the border of Albany Park on the city’s North Side. Floods caused damage to hundreds of structures since 2008.

North

Branch

Chicago

River

Area of

flooding

North

Shore

Channel

FOSTER

SPRINGFIELD

94

ELSTON

LAWRENCE

PULASKI

KIMBALL

KEDZIE

MONTROSE

Feet

1,000

ALBANY PARK

WHERE IS THE TUNNEL?

The tunnel will run for 1 mile under Foster Avenue.

Tunnel

FOSTER

HOW BIG IS IT?

The tunnel is 18 feet in diameter and 150 feet underground. Once finished a total of 69,000 cubic yards of rock will have been removed, leaving a tunnel that can hold 1.6 million cubic feet of water.

Concrete

14 inches

Tunnel

18 feet

HOW DOES IT PREVENT FLOODING?

If water rises over the bank, it flows into an inlet at Springfield Avenue at the North Branch of the river.

Down to

tunnel

Inlet

Floodwater

FOSTER

The water flows east, where it will come back to the surface and exit the outlet into the North Shore Channel near Albany Avenue.

Outlet

HOW IS THE TUNNEL BEING DUG?

Engineers are using an enormous hydraulic boring machine nicknamed “Keri,” built by German-based company Herrenknecht. It will cut the tunnel bit by bit. The machine was lowered down the outlet shaft and is boring the tunnel west toward Springfield Avenue.

PHOTO COURTESY CITY OF CHICAGO

HOW LONG WILL IT TAKE?

Engineers estimate the digging will take five months. That’s with the machine digging 6 days a week, 24 hours a day. After the tunnel is dug, it will be lined and waterproofed with concrete.

WHERE DOES IT FLOOD?

The North Branch flows along the border of Albany Park on the city’s North Side. Floods caused damage to hundreds of structures since 2008.

Area of

flooding

North

Branch

Chicago

River

North

Shore

Channel

FOSTER

ELSTON

KEDZIE

LAWRENCE

MONTROSE

ALBANY PARK

WHERE IS THE TUNNEL?

The tunnel will run for 1 mile under Foster Avenue.

Tunnel

FOSTER

HOW BIG IS IT?

The tunnel is 18 feet in diameter and 150 feet underground. Once finished a total of 69,000 cubic yards of rock will have been removed, leaving a tunnel that can hold 1.6 million cubic feet of water.

Tunnel

18 feet

Concrete

14 inches

HOW DOES IT

PREVENT FLOODING?

If water rises over the bank, it flows into an inlet at Springfield Avenue at the North Branch of the river.

Down to

tunnel

Inlet

FOSTER

The water flows east, where it will come back to the surface and exit the outlet into the North Shore Channel near Albany Avenue.

Outlet

Floodwater

HOW IS THE TUNNEL

BEING DUG?

Engineers are using an enormous hydraulic boring machine nicknamed “Keri,”built by German-based company Herrenknecht. It will cut the tunnel bit by bit. The machine was lowered down the outlet shaft and is boring the tunnel west toward Springfield Avenue.

PHOTO COURTESY CITY OF CHICAGO

HOW LONG WILL IT TAKE?

Engineers estimate the digging will take five months. That’s with the machine digging 6 days a week, 24 hours a day. After the tunnel is dug, it will be lined and waterproofed with concrete.

SOURCES: City of Chicago, Metropolitan Water Reclamation District of Greater Chicago, Chicago Department of Transportation